Glycosphinogolipids (GSLs) are cell surface components that have intrinsic interest as antigens and receptors, and which are useful for analysis of cell membrane organization and differentiation. A GSL molecule consists of a hydrophobic ceramide moiety and a polar carbohydrate chain which contains an antigenic determinant. We have purified and characterized antibodies to a number of GSLs. This proposal includes an extension of our basic immunochemical studies of GSLs, and projects in which the purified anti-GSL antibodies are used to study the distribution and functions of GSLs, and to identify differentiated lymphocytes. 1. Lymphocyte GSLs - Antibodies to six GSLs will be used to identify subpopulations of human lymphocytes. The functional properties of these subpopulations will be determined, and we will study the distribution and functions of these cells in patients with rheumatic and lymphoproliferative disease. 2. Erythrocyte GSLs -We have identified two antigens of the Lutheran blood group system as GSLs. These antigens will be purified, their structures will be determined and we will produce specific antisera to them. We will also complete the purification of new gangliosides that we have identified in human erythrocyte stroma. 3. Anti-GSL antibodies will be used to identify human GSL antigens in human-mouse hybrid cells that contain only one or two human chromosomes. These studies will make it possible to determine which human chromosomes carry genes that regulate the synthesis of these GSLs. 4. Purified anti-GSL antibodies will be used to study the ultrastructural localization and functions of gangliosides in the central nervous system.